JEREMY Corbyn has accused Boris Johnson of displaying silly arrogance after the foreign secretary said the European Union could "go whistle" if they made extortionate demands over Brexit.

The attack came as top bank executives in the City of London warned that the UK Government might have left it too late to convince major finance houses that it could strike a deal to soften the impact of Brexit before they started moving jobs to the continent.

At Westminster, Mr Johnson made his dismissive remarks in answer to questions from MPs over Britain’s proposed "divorce bill," which the country is expected to receive next week as Brexit negotiations resume in Brussels.

Jean-Claude Juncker, the European Commission President, has suggested the bill, which covers outstanding liabilities for programmes which the UK has signed up to as an EU member, as well as ongoing costs including staff pensions, could be around £50 billion; unconfirmed reports have claimed it could reach almost twice that figure.

During Foreign Office questions in the Commons, Philip Hollobone, a Conservative Eurosceptic, noted how the UK had made a net contribution of £209bn to EU coffers since joining in 1973 and asked the secretary of state: "Will you make it clear to the EU that if they want a penny piece more, then they can go whistle?"

Mr Johnson replied: "I'm sure that your words will have broken like a thunderclap over Brussels and they will pay attention to what you have said.

"He makes a very valid point and the sums that I have seen that they propose to demand from this country seem to me to be extortionate and 'to go whistle' is an entirely appropriate expression," declared the foreign secretary.

But speaking outside the Commons chamber, Mr Corbyn criticised the Tory frontbencher, saying: "It is ridiculous for the foreign secretary to approach important and serious negotiations with that silly, arrogant language that he so often employs.

"Treat people with respect and there's a fair chance you will be treated with respect in return. If you start on the basis of those silly remarks, what kind of response does he expect to get?"

On Thursday, the Labour leader is due to meet Michel Barnier, the EU's chief Brexit negotiator, in Brussels to set out his party's approach to Britain’s withdrawal and to hold "exploratory discussions" about the negotiations ahead.

He said Labour would "pay what we are legally required to pay" but nothing more.

But David Davis, appearing before the Lords EU committee, laughed off Mr Johnson's "go whistle" comments, telling peers: "Bluntly, I wouldn't worry. I mean you will have to get the Foreign Secretary here to explain his views if you really wanted to. I'm not going to comment on other ministers."

The Brexit secretary said the British strategy on the divorce bill was "not to pay more than we need to" and it would not accept the EU's "first claim" without going through it line by line.

"There will be a process of challenge going on here and that will happen and has started already in the negotiated process to establish whether or not we believe in that particular case they have made a legally defensible argument or not," he explained.

The UK's negotiating team led by Mr Davis is due to begin the first full round of negotiations with Mr Barnier on Monday.

Mr Johnson's comments came after Number 10 sources played down suggestions that Theresa May planned to walk out of the Brexit talks in September to show defiance over EU demands for a divorce bill worth tens of billions of pounds.

Meanwhile, top executives at five of the largest banks in London warned that because a transitional deal on leaving the EU was only likely to be agreed late on in talks with Brussels, banks were already relocating staff.

One senior executive at a global bank said: "The timeframe for when we wanted a transitional deal has already passed,” adding it had taken a decision to move hundreds of roles to continental Europe regardless of what the Government did.

James Bardrick, the UK head of US bank Citi, said the Government had been too slow to get any early deals with Europe and banks would have to be ready by September 2018.

"There's been a lot of talk and not a lot of action for a long time. I am anxious it is all a bit late," he complained.